Such collision protection devices, which serve for avoiding collisions of a pivotable hatch of a motor vehicle with obstacles, are already prior art. The interest in the present case is directed in particular to a tailgate of a passenger car, for instance a combi-van. It is already known to equip such a tailgate with sensors, which are designed to detect obstacles in the pivoting range or the opening range of the hatch during an opening movement. For instance the document DE 10 2008 029 223 A1 discloses a vehicle with a pivotable tailgate, which can be automatically opened by means of a control and drive unit. A sensor unit detects obstacles in the pivoting range of the hatch, and the opening of the tailgate can be stopped, if an obstacle is recognized prior to complete opening. The sensor unit in this connection is integrated into a light of the hatch.
A further collision protection device of the initially mentioned kind is known from the DE 10 2004 062 370 A1. Here a transmitter device and a receiver device are arranged in such a way on the tailgate that a radiating surface extends substantially in parallel and completely across the area of the tailgate. In other words the transmitter device has a transmission direction or capturing direction extending substantially in parallel to the tailgate.
In the subject matter according to document DE 102 35 925 A1 the sensor is arranged in such a way in the upper portion of the tailgate that it has a capture range directed at an angle downwards.
For detection of an obstacle in the pivoting range of the tailgate in the prior art commonly separate sensors are employed, which are used exclusively for this purpose. Such a solution, however, involves disadvantages with regard to the costs and the precious construction space. In the EP 0 968 863 A1 it is therefore suggested to employ ultrasonic sensors for detection of obstacles during the opening movement of the tailgate, which are part of the parking aid of the vehicle. These ultrasonic sensors support the driver in performing parking manoeuvres with the vehicle and moreover serve for the detection of obstacles in the pivoting range of the tailgate. What is to be regarded as disadvantageous about this prior art, however, is the fact that the ultrasonic sensors typically are not arranged on the tailgate, but on a bumper. In the case of most vehicles the ultrasonic sensors thus cannot be used for additionally capturing obstacles in the pivoting range of the tailgate.
The employment of a multifunctional sensor is further known from the DE 10 2007 049 256 A1. Here a sensor is employed, which is arranged and oriented on the tailgate in such a way that particles on the tailgate can be detected by capturing a light portion backscattered on the particles. Thus, by means of the sensor on the one hand a precipitation can be detected. On the other hand, the sensor is also used for capturing obstacles in the pivoting range of the tailgate during an opening movement and, if required, for stopping the opening movement. The capturing range of the sensor in this connection extends in parallel to the plane of the tailgate or in parallel to the plane of the pane. By this very set-up water drops on the plane of the pane can be reliably detected. Such an arrangement of the sensor, however, is only to some extent suitable for the function of the collision protection of the tailgate. With this sensor the exact capturing of the distance from the obstacle during the opening movement of the tailgate is not possible, and the opening movement can only then be stopped, when the obstacle enters the capture range of the sensor, which however has a very small height above the plane of the pane. It thus cannot always be guaranteed that the tailgate is stopped early enough before colliding with the obstacle.
It is the task of the invention to show a solution as how to facilitate in the case of a collision protection device of the initially mentioned kind an effective and reliable collision protection for the pivotable hatch of the motor vehicle without requiring much effort.